Field of the Invention
The present invention relates to a sheet feeding apparatus for feeding a sheet supported on a tray to a position that differs from the tray, and an image forming apparatus adopting the sheet feeding apparatus.
Description of the Related Art
Various types of electro-photographic or ink-jet image forming apparatuses are known. In these types of apparatuses, there are demands to perform maintenance operations without interrupting print jobs, with the aim to improve productivity.
An exemplary image forming apparatus accepts sheets formed of paper, plastic, and other materials as recording materials, and includes a sheet feeding apparatus to feed the sheets of such recording materials to the image forming apparatus. This type of sheet feeding apparatus may include a detachable cassette storing a large number of sheets, and a manual sheet feeding apparatus where sheets are mainly manually supplied from outside of the apparatus body.
The sheet feeding apparatus for manual sheet feeding includes a tray supported on the apparatus body and capable of being opened and closed. The tray can support one sheet or a plurality of sheets to be set manually. The sheet supported on the tray can be fed to an image forming mechanism provided inside the apparatus by a conveyance mechanism including a pickup roller arranged to face the tray, a conveyance roller, and a separation roller.
The tray is opened with respect to the apparatus body or a cover member by a swing mechanism, for example, and moved to a sheet feed position where the above-described manual sheet feeding is performed. Further, the tray is closed to a storage position by the same swing mechanism when the tray is not used, so that a surface of the tray forms approximately a same plane as the surface of the apparatus body or the cover member.
As regard the sheet feeding apparatus for manual sheet feeding arranged as above, there is a case where maintenance operation of the sheet conveyance mechanism including the pickup roller, the conveyance roller and the separation roller is required. There are demands for an arrangement where maintenance operations such as roller replacement can be performed easily, for example from an upper side of the tray supporting the sheet, without opening a door on the apparatus body or removing a number of other components.
However, an opening angle of the tray in a sheet feed position where the tray is at an opened state is often set to such an angle where the supported sheet is inclined downward toward the sheet conveyance mechanism composed of various rollers, in order to realize smooth feeding of sheets. Since the tray is opened at such a relatively small angle that is inclined downward toward the sheet conveyance mechanism, it has been difficult to ensure sufficient work space for roller replacement and the like.
It may be conceivable to adopt a method enabling maintenance operations such as roller replacement to be performed from the tray side by removing the tray of the sheet feeding apparatus or by changing the angle of the tray to expand the work space at the time of maintenance, without opening the apparatus body door. For example, a configuration of removing links and stoppers of a tray angle retention member may be considered as a method for changing the tray angle. Meanwhile, U.S. Pat. No. 8,857,812 discloses such a configuration using an elastic member that can be adopted for changing the opening angle of the tray in multiple steps.
However, the configuration taught in the above document requires continuous application of external force toward the swinging direction of the tray to change the angle of the tray from a position where sheets are fed to a position where maintenance is performed. Therefore, the tray angle may be changed by the weight of the sheets supported on the tray or unintentional touching of the tray by a user, and problems such as sheet feed failure and multiple sheet feed may occur. Further, if a method of removing the tray angle retention member is adopted, the removing operation may require tools, or the removed components may be lost, which cases lead to deterioration of maintenance performance.